LESION OF DIFFERENT REGIONS OF THE CEREBRAL HEMISPHERES. 531 
The subsequent destruction of the prefrontal regions caused symptoms which, 
though very transient, were yet of important significance. These were rapid lateral 
oscillations of the head, lasting only a few hours, apparent inability to move the head 
except en masse with the trunk, and ptosis of the right eye. None of these symptoms 
were, however, at all discoverable on the third day, and from this time onwards the 
animal exhibited no discoverable defect, either as regards the movements of its head 
and eyes, or otherwise. It is to be noted in this case that a considerable portion of 
the base of the superior frontal convolutions still remained uninjured, though the 
prefrontal regions were almost entirely destroyed. 
Apart from a degree of dulness or apathy—and this as time went on not 
particularly observable—there was nothing in the animal’s behaviour at all remark¬ 
able or appreciably abnormal. 
But the important anatomical fact described in connexion with Experiment 22 was 
here also noted, viz. : descending degeneration of the mesial bundles of the internal 
capsule and crus cerebri, as far as the pyramidal tracts of the pons. 
These degenerated fibres were, in the internal capsule, of clearly different dates. 
The older, which were sclerosed and deeply stained, might reasonably be regarded 
as in relation with the older of the lesions in the frontal lobes, viz. : those at the base 
of the frontal convolutions ; while the others situated nearer the middle line and less 
deeply stained than normal, might reasonably be connected with the later prefrontal 
lesions. Their position agrees exactly with that of the degenerated bundles in 
connexion with the prefrontal lesions of Experiment 22. 
The ultimate destination of the degenerated tracts was not determined, but they 
do not appear to pass into the anterior pyramids of the medulla oblongata. 
General Results. 
These experiments on the frontal lobes show a remarkable absence of any discover¬ 
able physiological symptoms in connexion with the almost entire destruction of the 
prefrontal regions, or anterior two-thirds of the frontal convolutions ; and only tem¬ 
porary impairment or paralysis of the lateral movements of the head and eyes as 
the result of lesions, extensively destroying the cortex at the base of the superior 
and middle frontal convolutions (centre 12). In none of the cases, however, was the 
destruction of this centre on both sides quite complete. It was most extensive in 
Experiment 21, in which also the prefrontal regions were removed. 
This case, however, owing to the sudden death of the animal shortly after the 
operation, did not afford much opportunity for observation of the effects of the lesion. 
But negative facts of great importance were demonstrated in this case. There was 
no affection of sensation general or special, and the limbs, face, and tail were capable of 
voluntary movement. 
There was apparent total paralysis of the lateral movements of the head and eyes, 
and inability to maintain the upright position, though backward and forward move- 
